Field of the Invention
The present invention relates to an image forming apparatus with an operational mode allowing a so-called power-saving operation as well as to a controller for controlling the power-saving operation of the image forming apparatus. More specifically, the present invention relates to an image forming apparatus having a function of controlling time from completion of a work before a power saving mode is entered, and a controller therefore.
Description of the Background Art
As one type of image processing apparatuses as electronic equipment, an image forming apparatus for forming an image on a sheet of paper (typically a copy machine) has been introduced to many places of business (companies and offices). In such a place of business, it is becoming a common practice to have an image forming apparatus having a printer function or copy function connected to a network and to share the apparatus by a plurality of users. An MFP (MultiFunction Peripheral) as one type of such image forming apparatus has a plurality of basic operational modes including copy mode, facsimile mode, network-compatible printer mode and scanner mode. In such an image forming apparatus, each user sets an operational mode and sets a function such as double-sided printing or collective printing (2-in-1 of printing two pages on one sheet, or 4-in-1 of printing four pages on one sheet), and thereby forms an image on recording paper in a desired manner. Appropriate combinations of these functions are used increasingly these days.
Let us consider a digital image forming apparatus provided with an image forming unit utilizing electrophotography process. In such an image forming apparatus, a toner image reproduced on a photoreceptor is transferred to a sheet of recording paper. A heating and fixing unit has a heat source such as a heater, and fixes the toner that has been transferred to the sheet of recording paper on the sheet, with prescribed temperature and pressure. Therefore, in order to provide an environment allowing image formation at any time, it is necessary to keep the heating and fixing unit at a constant temperature. This means that power conduction to the heater must be controlled continuously. Such a control naturally leads to a problem of increased power consumption. Particularly, a heater needs much electric power and, therefore, it poses a significant problem from the viewpoint of energy saving. Reduction of power consumption in companies and offices is emphasized recently and, therefore, constant need of such big electric power is undesirable.
In view of the foregoing, it may be possible to control power conduction to the heating and fixing unit taking into account operational status of the image forming apparatus while it is powered on. If power conduction to the heating and fixing unit is reduced too much, however, there arises a problem that image formation cannot be started immediately even when power conduction to the heating and fixing unit is resumed for image formation. This is because the temperature of heating and fixing unit has been reduced. An image cannot be formed before the heating and fixing unit attains to a prescribed temperature, and the user is kept waiting. Therefore, it is not preferable to shut-off power conduction to the heating and fixing unit too early after the end of operation of the image forming apparatus.
On the other hand, depending on the time of day or time slot, the apparatus may be used very frequently or may be left idle and kept in a standby state for a long time. If the operational status of the image forming apparatus is monitored carefully and the time before power conduction to the heating and fixing unit is shut-off is determined appropriately, power consumption may possibly be further reduced.
As a solution to such a problem, Japanese Patent Laying-Open No. 2007-30325 (hereinafter referred to as '325 Reference) discloses a printing device in which data is accumulated by obtaining number of printings per each time slot while the device is powered-on, and transition time to the power saving mode is determined based on the number of printings of each time slot included in the accumulated data.
FIG. 1 shows an example of wait time per hour of the image forming apparatus, and FIG. 2 shows an example of change in the number of outputs and the number of jobs per hour. As shown in FIGS. 1 and 2, the wait time, the number of outputs and the number of jobs per hour have prescribed patterns. Such patterns, however, may vary department by department, or may vary seasonally. The patterns may also vary dependent on the day of the week.
The printing device disclosed in '325 Reference learns the transition time to the power saving mode based on the history of printing, and the printing device is controlled such that the time before suspension is made shorter in the time slot when the number of printing is small, and the time before suspension is made longer in the time slot when printing is done relatively frequently. Such a control reduces the possibility that the printing device is in the suspended state and that it takes long before an image is formed, when use of the printing device is started.
Here, it is noted that depending on the place where the image forming apparatus is installed, the day and the time of day (time slot) when the business peaks is known in advance. If the transition time to the power saving mode is set short in the day and the time of day when the business peaks, business efficiency lowers. Therefore, it is preferred that the transition time to the power saving mode is manually settable, to prevent the transition time to the power saving mode from being set too short in such a specific day (hereinafter also referred to as a specific day) and specific time of day (hereinafter also referred to as a specific time slot).
For instance, Japanese Patent Laying-Open No. 2005-71269 (hereinafter referred to as '269 Reference) discloses an image processing system in which the power saving mode of a specific day and specific time slot can be set manually based on calendar data. It is possible to activate the learning function as described in '325 Reference and to manually set the “specific day and specific time slot” as disclosed in '269 Reference to cause the apparatus in a specific power saving setting (transition time to the power saving mode) in the specific day and the specific time slot, so as to cope with the peak business day of each month and thereby to prevent decrease in business efficiency.
If the operation patterns of an image forming apparatus are well understood by the user, it may be possible to combine the manual setting with learning, as described in '269 Reference, to reflect the operational status of the image forming apparatus. In that case, however, if the relation between manual setting and learning is not successfully established, learning accuracy possibly degrades. Such a problem is not described in '269 Reference. The manual setting itself is not necessarily easy if the actual situation is to be accurately reflected. If the manual setting is not very accurate, energy saving effect cannot be attained. If accuracy of manual setting is to be increased, it becomes necessary to accurately grasp the operational status of the image forming apparatus, and the burden on a person in charge becomes heavier.